JPH0273883A - Liquid crystal device - Google Patents

Abstract

PURPOSE:To provide a liquid crystal device having a dimming layer composed of a specified nematic liquid crystal material forming the continuous phase and transparent solid materials dispersed therein, capable of drive at a low voltage, requiring no use of a polarizing plate and capable of scaling up. CONSTITUTION:An objective liquid crystal device in which a dimming layer supported between bases is composed of a nematic crystal material containing (A) a compound represented by formula I (R is 1-10C straight chain alkyl or straight chain alkoxy; Formula II is formula III or formula IV) and (B) a compound expressed by formula V (R is 1-10C straight chain alkyl; X is H, F or Cl) and (B) transparent solid materials consisting of a synthetic resin, etc., dispersed therein, preferably in a three-dimensional network state.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a thin film containing a liquid crystal that can be formed over a large area. , blocking, and transmitting can be controlled electrically, and are used as screens to block the view in building windows and show windows, as well as curtains for lighting control, as well as to display characters and figures, and to provide high-speed response. Therefore, by electrically switching the display,
Used as display devices such as advertising boards, information boards, decorative display boards, etc.

(Prior art) Liquid crystal display elements have conventionally been TN using nematic liquid crystal.
type and STN type are in practical use.

Also, devices using ferroelectric liquid crystals have been proposed. These require polarizing plates and also require alignment treatment. On the other hand, as a method for manufacturing large, inexpensive liquid crystal devices that are bright and have good contrast without requiring these devices, a method is known in which liquid crystal encapsulation is used to disperse liquid crystal droplets in a polymer and then turn the polymer into a film. It is being Here, gelatin, gum arabic, polyvinyl alcohol, etc. have been proposed as encapsulating substances (Japanese Patent Publication No. 58-501631, USP 443).
No. 5047).

In the technology disclosed in the above specification, if the liquid crystal molecules encapsulated with polyvinyl alcohol have positive dielectric constant anisotropy in a thin layer, the liquid crystal molecules can be encapsulated in the presence of an electric field. are aligned in the direction of the electric field, and when the refractive index n0 of the liquid crystal and the refractive index n2 of the polymer are equal, transparency is exhibited. When the electric field is removed, the liquid crystal molecules return to their random alignment and the refractive index of the liquid crystal droplet deviates from no, so the liquid crystal droplet scatters light at its interface and blocks the transmission of light, so the thin layer becomes cloudy. do. In addition to the above-mentioned techniques, there are several other known techniques for making thin films of polymers containing dispersed encapsulated liquid crystals.
No. 1-502128 discloses a liquid crystal dispersed in an epoxy resin, and JP-A-62-2231 discloses a liquid crystal dispersed in a special ultraviolet curable polymer.

(Problems to be Solved by the Invention) Important characteristics required in the practical application of large liquid crystal devices such as those described above are (i> ability to drive at low voltage (11) sufficient contrast (iii)
) Time division driving may be possible.

In particular, (1) and (iii) are extremely important characteristics in order to make the driving part of the device inexpensive.

However, to date, (i) to (iii)
) A liquid crystal device that does not require a polarizing plate has not been fabricated.

The inventors of the present invention have conducted extensive studies on the preferred combination of the structure of a liquid crystal device and the chemical structure of the liquid crystal material used in the device, and have found that it can be driven at a much lower voltage than conventional large liquid crystal devices, and that it can be driven with a polarizing plate. We have succeeded in creating a liquid crystal device that can be made larger without the need for the use of.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides a liquid crystal device described below.

That is, the liquid crystal device according to the present invention has two substrates each having an electrode layer and at least one of which is transparent, and a light control layer supported between the substrates, and this light control layer has the following general structure. It consists of a nematic liquid crystal material containing a compound of formula (1) and a compound of the following general formula (IT) and a transparent solid substance, the liquid crystal material forming a continuous phase, and the transparent solid substance forming the liquid crystal material. It is a liquid crystal device characterized by the fact that it is dispersed in the liquid crystal.

Compounds represented by general formula (1) general formula (II) (wherein R represents a linear alkyl group having 1 to 10 carbon atoms, and X represents a hydrogen atom, a fluorine atom, or a chlorine atom) (Hereinafter referred to as the compound of formula (II)).

In this device, the substrate may be a rigid material such as glass, metal, etc., or a flexible material such as a plastic film. Two substrates can be placed facing each other with an appropriate distance between them. Also, at least one of them is transparent, and the second one is transparent.
The light control layer supported between the layers must be visible from the outside world. However, complete transparency is not required; if the liquid crystal device is used to act on light passing from one side of the device to the other, the two substrates Both provide appropriate transparency. Appropriate transparent or opaque electrodes may be disposed on the entire surface or part of the substrate depending on the purpose.

A liquid crystal material and a transparent solid component are interposed between the two substrates. Incidentally, it is desirable to interpose a spacer for maintaining the distance between the two substrates according to a conventional method, as in well-known liquid crystal devices.

Liquid crystal materials require the formation of a continuous phase between two substrates. If the ratio of liquid crystal material components is low, it is difficult to form a continuous phase. The proportion of the liquid crystal material in the light control layer components is preferably 70% by weight or more, and even more preferably 70 to 90% by weight.
% by weight (hereinafter, % means % by weight).

The transparent solid component interposed in the continuous phase of this liquid crystal material is
It may be dispersed in the form of particles, but preferably has a three-dimensional network structure. In any case, it is essential to form an optical interface with the liquid crystal material and to cause light scattering to occur. Its transparency can be determined appropriately depending on the purpose of use of the device, and its solidity is not limited to being rigid, but must be flexible, pliable, and elastic as long as it can meet the purpose. Also good. In the case of particles, if the particles are too large or small compared to the wavelength of light, light scattering properties cannot be expected, but particles of appropriate size and shape can be selected depending on the purpose.

Synthetic resins are suitable as these transparent solid components. Ultraviolet curable monomers or oligomers are preferred as those that provide a three-dimensional network structure.

These liquid crystal devices can preferably be manufactured as follows.

That is, between two substrates each having an electrode layer and at least one of which is transparent, the above-mentioned liquid crystal material as essential components, an ultraviolet curable polymer-forming monomer or oligomer, and a polymerization initiator and a chain as optional components. The liquid crystal material forms a continuous phase by irradiating ultraviolet light through a transparent substrate in the presence of a solution consisting of a transfer agent, a photosensitizer, a dye crosslinking agent, etc., thereby polymerizing the monomer or oligomer. This is a method for manufacturing a liquid crystal device in which a transparent solid synthetic resin component in the form of a dimensional network is dispersed in a continuous liquid crystal phase.

In this method, the ultraviolet curable polymer-forming monomer or oligomer that is an essential component may be one that forms a three-dimensional network in the continuous phase of the liquid crystal material by the irradiated ultraviolet rays. Good examples of molecule-forming monomers are trimethylolpropane triacrylate, tricyclodecane dimethylol diacrylate, polyethylene glycol diacrylate, polypropylene glycol diacrylate, hexanediol diacrylate, neopentyl glycol diacrylate,
Tris(acryloxyethyl)isocyanurate and the like.

Similarly, a good example of a polymer-forming oligomer is caprolactone-modified hydroxypivalic acid ester neopentyl glycol diacrylate.

Optional components include polymerization initiators, chain transfer agents, photosensitizers, dyes, crosslinking agents, etc., and can be appropriately selected depending on the types of monomers, oligomers, etc. and the performance of the desired liquid crystal device. can.

In particular, the combined use of a chain transfer agent can be extremely effective depending on the type of monomer or oligomer, preventing the resin from becoming too cross-linked, thereby making the liquid crystal material more responsive to electric fields, and lowering voltages. Drivability is demonstrated. Good examples of chain transfer agents are butanediol dithiopropionate, pentaerythritol tetrakis (β-thiopropionate), triethylene glycol dimercaptan, and the like. The amount of chain transfer agent added varies depending on the type of monomer or oligomer used, but if it is too small, the effect will be weak, and if it is too large, the opacity of the device will decrease and the contrast of the display will deteriorate. Its effective amount is
Possible amounts are 0.05-30%, based on monomer or oligomer, but 0.1-20% is preferred.

In order to support a solution containing each of these components between two substrates, this solution may be injected between the substrates, but it may be applied onto one substrate using a coater such as a spinner.
Then, the other substrate may be placed on top of the other substrate.

Curing of an uncured solution can be accomplished by irradiating a suitable dose of ultraviolet light through the transparent substrate. Depending on the type of nanatsuma or oligomer or optional ingredients,
Heat or electron beams can also be used instead.

The thickness of the light control layer is usually adjusted to a range of 5 microns to 30 microns.

A liquid crystal device configured in this manner enables time-division driving, which was not possible with conventional droplet dispersion type liquid crystal devices, and also has a lower driving voltage than conventional droplet dispersion type liquid crystal devices. High contrast and fast response speed. For example, while a conventional droplet dispersion type liquid crystal device requires a driving voltage of 60 V or more in effective value, and in many cases 100 V or more, the liquid crystal device of the present invention requires a rise response time of 3 with a driving voltage of about 20 V. ~4 msec and a fall response time of 3-4 msec are achieved.

(Example) Examples of the present invention will be shown below to further specifically explain the present invention. However, the present invention is not limited to these examples.

Example 1 19.8% by weight of trimethylolpropane triacrylate as a polymer-forming monomer (the same applies hereinafter), 0.2% of 2-hydroxy-2-methyl 1-phenylpropan-1-one as a polymerization initiator, and liquid crystal material 80% of the liquid crystal (A) described below was mixed as a spacer, and an average particle size of 1 was added as a spacer.
Add a small amount of 0pm alumina powder, insert it between two 20cm x 20cm ITO glass plates, and irradiate it with ultraviolet light.
The monomer was cured (polymerized). The curing conditions were as follows: The liquid crystal device was heated using a metal halide lamp (80W/cfIl).
) at a speed of 3.5 m/min, and was irradiated with ultraviolet rays. The applied energy corresponds to 500 mJ/cm2. The electrode spacing of the device is 11 μm.

When a cross section of the light control layer formed between two glass plates was observed using a scanning electron microscope, a three-dimensional network of polymers was observed.

The obtained liquid crystal device has a threshold voltage of 1°=7.7V, V. -14,9V, contrast =
1:20, the rising response time was 2.7 msec, the falling response time was 368 msec, and the number of time division lines N was 3.0.

(1) Liquid crystal (A) Composition transition temperature 68.0°C (N-I point) 13°C (C-N point) Refractive index n, = 1.719 n, = 1.516 △n = 0.203 Threshold Value voltage (Vtl,) 1.16 V viscosity at 20℃
61.1c, p.

(2) Number of time-division drive lines N,,, = ((α” +1)/ (α2-1)) Also, α-■, ./V +.

(3) The light transmittance of the device when no voltage is applied is 0%,
When the light transmittance at which the light transmittance does not change as the applied voltage increases is 100%, the applied voltage at which the light transmittance becomes 90% is V. , the applied voltage when the light transmittance becomes 10% is 1°.

(Effects of the Invention) As described above, the present invention is a large-area, thin-film liquid crystal device that can be driven at a low voltage of about 15 V, and has a rise response time of 3 to 30 volts even at such a low voltage. 4m
The response speed is as fast as seconds, and the contrast between transparent and opaque is approximately 1
= 20, has a threshold value, and is capable of time-division driving with a duty of 1/3. Therefore, it becomes extremely easy to adjust the lighting, adjust the visual field, and make large-scale displays for advertisements, etc., and furthermore, the manufacturing of such liquid crystal devices becomes extremely easy and inexpensive.

Claims (1)

[Scope of Claims] 1. Two substrates each having an electrode layer, at least one of which is transparent, and a light control layer supported between the substrates, wherein the light control layer has a general formula ▲ mathematical formula, chemical formula, or table. etc. ▼ (In the formula, R represents a linear alkyl group or a linear alkoxyl group having 1 to 10 carbon atoms, and ▲ includes mathematical formulas, chemical formulas, tables, etc.) ▼ indicates ▲ mathematical formulas, chemical formulas, tables, etc. There are ▼ or ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼.) Represents the compound represented by the general formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (In the formula, R is a straight chain with 1 to 10 carbon atoms. (X represents a hydrogen atom, a fluorine atom or a chlorine atom) and a transparent solid substance, the liquid crystal material forming a continuous layer and the transparent A liquid crystal device characterized in that a solid substance is dispersed in the liquid crystal material. 2. The liquid crystal device according to claim 1, wherein the liquid crystal material accounts for 70% by weight or more of the components of the light control layer. 3. The liquid crystal device according to claim 1, wherein the transparent solid material is made of synthetic resin. 4. The liquid crystal device according to claim 1, wherein the transparent solid substance is dispersed in the liquid crystal material in the form of particles or a three-dimensional network. 5. The liquid crystal device according to claim 1, wherein the light control layer has a thickness of 5 to 30 microns.